This invention relates to a method for forming a coated film and an apparatus therefor, and more particularly to a method for forming a coated film on a desired region of an inner peripheral surface of a cylinder and an apparatus therefor.
In the prior art, an adhesive applying apparatus typically includes a cylindrical container (cylinder) which receives an adhesive curing upon contact with air, a nozzle arranged at a distal end of the container and a piston member arranged in an opening formed at a rear portion of the container, wherein the piston is driven toward the nozzle to discharge the adhesive from a distal end of the nozzle. In the conventional adhesive applying apparatus thus constructed, in order to prevent air from intruding from an outside of the apparatus through a gap between the piston and the adhesive thereinto immediately before starting of adhesive applying operation of the apparatus, an inner peripheral surface of the container is coated on a portion thereof at which the piston is initially arranged with a seal material so as to extend over a whole circumference thereof. In the prior art, such application of the seal material (thermoplastic material) to at least a part of the inner peripheral surface of the cylinder in a manner to extend over a whole circumference thereof is carried out by inserting a nozzle into an inner space of the cylinder to spray the seal material onto the portion of the inner peripheral surface. Also, such a conventional seal material applying apparatus uses a gear pump for generating a pressure required to feed the seal material in the form of a molten paste to the nozzle.
However, the above-described conventional techniques of forming an applied or coated film of the seal material by spraying cause the molten paste to be scattered to an undesired region of the inner peripheral surface of the cylinder other than a desired one thereof, leading to a failure to form the coated film on the desired region. In order to avoid the problem, techniques of carrying out spraying of the adhesive by means of a mask are proposed. Also, the paste applying apparatus using the gear pump is hard to control a pressure under which the thermoplastic material is discharged from the nozzle, to thereby fail to form the coated film into a uniform thickness.